Electric time fuze



March 1, 1960 H. E. RUEHLEMANN 2,926,610

' ELECTRIC TIME FUZE Y Filed Aug. 1, 1951 T) INVENTOR.

H. E. RUEHLEMANN BY 6367M" ATTYS.

2,926,610 ELECTRIC TIME FUZE Herbert Ernst Ruehlemann, Silver Spring,Md., assignor to the United States of America as represented by theSecretary of the Navy This invention relates to a fuze and moreparticularly to an electrically controlled fuze for use in an ordnancemissile such, for example, as a projectile, rocket, bomb or the like forexploding the missile in predetermined time delayed relation withrespect to impact thereof with a target or in time delayed relationautomatically with respect to subsequent impacts of the missile withsubsequent targets after penetration ofa first target surface.

Heretofore, fast and slow burning pyrotechnic elements have beenemployed in ordnance missiles for delaying the ignition and explosion ofthe main charge therein after impact of the missile with-a target. Suchtime delay elements have not proven to be-entirely satisfactory for thereason that once the fuze is assembled the time delay period remainsfixed and can not be varied or adjusted at the time of firingor-launching of the missile or automatically controlled upon impact ofthe missile with a target thereby rendering such missiles uselessparticularly when used against certain types of targets. I

The present invention provides basic advantages over the prior artpyrotechnic time delay elements for the reason that the new and improvedarrangement provides means for selecting the desired time delay periodin accordance with the type of target subjected to attack and in whichadditional means are employed whereby the time delay period iscontrolled automatically with respect to subsequent impacts of themisisle with subsequent targets after penetration of a first targetsurface.

An object of the present invention is to provide a new and improvedelectric fuze for an ordnance missile in which means are provided forautomatically obtainingvarious delayed ignitions of the igniter elementarranged within the fuze depending upon the type of target subjected toattack.

Another object of the invention is the provision of a new and improvedelectric fuze for an ordnance missile in which storage means areprovided for causing the missile to be fired at different time intervalsafter. impact thereof with a target by varying the initial charge of thestorage means. 1

A further object of the invention is the provision of a new and improvedRC delay circuit arrangement for an ordnance missile whereby an optimumdelay is manually selectable and in addition thereto the circuitresponse is a function of the actual impact.

,A still further object resides in the provisionof an electric time fuzein which the difference in the conductivity of a rectifier in reversedirections is'utilized to control the firing of the fuze. Y

Other objects and many of the attendant advantages of the invention willbe readily appreciated as the same becomes better understood byreference to'the following detailed description when considered inconnection with embodiment of the present invention; and

tatcs Patent I 2,926,610 Patented Mar. 1, 1960 ice ' Figs. 2, 3 and 4are views in diagrammatic form showing alternate arrangements of thedevice of Fig. 1.

"Referring now to the accompanying drawings in which like referencecharacters designate corresponding parts throughout the several viewsand more particularly to Fig. 1 thereof, the numeral 10 generallydesignates a new and improved RC time delay fuze arrangement comprisalaunching rack, as the case may be, it being understood,

however, that by varying the values of the charge in condenser Cl alonger or-shorter time delay period may be series with respect to eachother an electroresponsivedetonator or igniter I, rectifier REC, coldcathode diode or glow tube D, and condenser 'C3. g

Rectifier-REC may be of any suitable type such, for

example, as germanium 'rectifiers, having a forward-resistance of theorder of lOohms and a reverse resistance in the order of 100,000 ohms.Ig'niter I preferably has a resistance in the ratio of 1 to 10,000 withrespect to the reverse resistance of the rectifier for reasons morefully to appear hereinafter in the description of the operation of thecircuit of Fig. l.

Glow tube D in a specific circuit arrangement has a breakdown potentialin the order of 100 volts and a conduction sustaining potential in theorder of 60 volts, the tube breaking down and conducting when thevoltage across the elements exceeds approximately 100 'volts and thetube being extinguished when the voltage .thereacross falls belowapproximately 60 volts.

T forward'force resulting from impact of the, supporting missile with atarget.

During this impact of the missile with a target, switch SW closes inresponse thereto and condenser C2 is chargedsubstantiallyinstantaneously by the normally charged condenser C1.(Concurrently therewith current from con- "R and when a predeterminedperiod of time has elapsed denser-Cl passes through resistor R and alsothrough path 13 whereupon condenserC3 is charged through igniter I,rectifier REC and diode D in series therewith. By the specificarrangement of the rectifier in the circuit as disclosed the highresistance is effective during the trans{ fer charging period from C1 toC3. and thus the voltage dissipated across the igniter is low in valueand therefore such voltage is of insufficient strength to fire theigniter.

When switch-SW opens following the impact, the switch being open, forexample, for an interval in the order of one millisecond, the chargeoricondens'erCZ discharges through resistor R and through path 13 thuscon-- tinuing the charging of condenser C3. until the difference in thevoltages on condensers C2 and C3 becomes less than the conductionsustaining potential of tube D, this being volts in the specific exampleaforementioned,

whereupon the tube is extinguished and further charging of condenser C3ceases. I

Condenser C2 continues to discharge through resistor following theimpact and corresponding to a selected time delay period controlledprincipally by the time constant, RC, of condenser C2 and resistor R,the charge in C2 is drained sufiiciently to allow the diode D to conductagain but this time in the reverse direction, the difference in thevoltages of condensers now being equal to or exceeding the breakdownpotential of tube D of approximately 100 volts, and thus when thisreverse transfer charging process occurs the voltage dissipated at theigniter I is of a high degree owing to the low forward resistance of therectifier and is of sufficient strength to fire the igniter thereby toexplode the missile.

However, it will be apparent that by varying the voltage in the storagecondenser C1, the delay time at which the fuze will function may bevaried, the charge transferred to condenser C2 being of more or lessvoltage depending on the voltage of condenser C1, a higher voltageresulting in a lower delay time, for example, as in the case of priorart RC time delay circuits. It will be obvious, however, that theselection of the delay time period is determined in accordance with thekind and structural arrangement of the target subjected to an attack.

Furthermore, it will be understood that during the period of time thatthe switch SW is closed, the time constant for discharging the condenserC2 through resistor R is increased by the capacity of C1 therebyincreasing the delay time before the ignition of the igniter occurs.Thus should the projectile strike and penetrate a target composed ofthick material such, for example, as a fortification or armor plate of aship, the impact switch SW remains closed a longer period of time thanwhen the missile strikes a target composed of thin material. Thus itwill be apparent that the ignition time of the igniter will beautomatically increased by the resulting higher time constant (Cl+C2)R.

An additional effect may be obtained by the aforesaid circuitarrangement, particularly when the missile is used for the destructionof other targets such, for example, as a house or ship or the like, andin such cases the missile is adapted to penetrate the roof and floorstructure of a house target or several armor plates of a ship, as thecase may be. It will be apparent from the foregoing, that by selecting avoltage which results in a delay time longer than the time necessary forthe projectile to strike and penetrate the aforesaid roof structure orone of the plates, as the case may be, and to continue on through thefloor structure or second plate structure, the circuit will not causethe fuze to function and explode the missile at the time of the secondimpact for the reason that when the second impact occurs, the switch SWis closed again in response thereto whereupon condenser C2 which hasbeen substantially discharged in response to the first impact will berecharged by C1 a predetermined amount and thus during the aforesaidsecond charging cycle ignition of the igniter I is delayed automaticallyin response to the aforesaid second impact.

Furthermore, the aforesaid fuze arrangement may be advantageouslyemployed in submarine warfare. When used against such targets arelatively low charge in condenser Cl results in a longer delay, for thereason, that upon water impact switch SW is closed, and will remainclosed during the travel of the missile through the water toward thesubmarine target and thus a longer delay time period will occur in caseof a near-miss whereupon the likelihood of the missile being exploded ator near the target will be greatly increased. In such case, switch SWbeing closed, the voltage on condenser C3 rises above the voltage oncondenser C2 in an amount equal to or exceeding the breakdown potentialof glow tube D when the predetermined time delay has elapsed and thecharge on condenser C3 is discharged in the forward direction throughthe rectifier REC and through the detonator whereupon the fuze is fired,the charge on. condensers Cl and. C2 being, dissipated through resistorR. and. passed;

in part to condenser C3 whereas the charge simultaneously developed incondenser C3 is retained therein until reakdown of the glow tube.However, should the missile strike the submarine during the waterdescent thereof the impact switch SW will open in response to thedeceleration of the missile as the missile strikes and penetrates theouter shell of the submarine and thus the time constant is diminishedthereby causing automatic ignition of the igniter in a shorter period oftime after impact and penetration of the target by the missile.

Referring now to the fuze arrangement of' Fig. 2, an additional delayaction is accomplished by employing a normally closed switch SW2 inaddition to switch SW, Fig. 1, the switch being shunted across a portionof'a resistor R2. Such delay action occurs as the switch is loved fromthe initial closed position to an open position and thence back to theinitial position before the charging circuit from C2 through resistor R2and to C3 is completed.

Assume, for example, that R2 is center tapped at the connection with SW2and is twice the resistance of R of Fig. 1. When switch SW closes andswitch SW2 opens On impact, the time constant of the charging circuit is(C1+C2)R2=(C1+C2) 2R=2(C1+C2)R which is twice the corresponding timeconstant for Fig. 1. Accordingly, the time required to place the samecharge on condenser C2 when switch SW opens in the case of Fig. 2 isapproximately twice that required in Fig. 1. However, when switch SW isclosed forthe same interval in each case, the resulting voltage-on C2 inFig." 2 is correspondingly less and a longer time delay results and thecircuit of Fig. 2 operates in the same manner as Fig. 1 when switch SW2becomes closed following the impact.

In reference to Fig. 3 of the drawings the arrangement and operationthereof is substantially identical as that of Fig. 2 except that adouble action switch SW3 is sub stituted for switches SW and SW2, theoperation of the circuits of Figs. 2 and 3 otherwise being the same.

In the arrangement of Fig. 4, resistors R and R3 are employed as delayaction means, resistor R3 is disposed between condensers C1 and C2 fordelaying the build up of condenser C2 by C1 as the switch SW functionsto a closed position as hereinbefore set forth. By reason of thisarrangement, condenser C2 is charged to a lower voltage than in Fig. lfor the same closure time of switch SW with the result that a longerdelay time is provided, it being recalled that the delay time is longerfor lower voltages and shorter for higher voltages.

It will be obvious in view of the foregoing that by selecting the propervalue of the initial charge, and the values of capacitance andresistance the desired time delay may be obtained. Furthermore, thepresent invention provides a new and improved RC delay fuze arrangementthe time constant of which may be changed by varying thesize of theresistor or resistors, as the case may be, or by varying the size ofboth the resistors and condensers, and in which an optimum delayismanually selectable, and in addition thereto the circuit response is afunction of the actual impact of the missile with a target.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

1. An electric time fuze comprising, in combination, an electricalenergy source having a decreasing potential level thereacross, anelectrical circuit connected across said source and includingan.electroresponsivedetonator;

a glow tube, an energy storage device and a rectifier having low energyconductance in one direction of an amount insuflicient to effectignition of said detonator whereby the energy passed therethrough fromsaid source is stored in said storage device until the potential acrosssaid storeage device becomes substantially equal to the sustainingpotential of said glow tube, said rectifier having high energyconductance in the opposite direction for discharging the energy storedin said device through said detonator in an amount sufiicient to firesaid detonator when the potential across said device exceeds thepotential across said source by an amount necessary to render said glowtube conductive.

2. An electric time fuze of the character disclosed for use in a missilecomprising, in combination, a first normally discharged condenser, asource of electrical energy, impact responsive switch means formomentarily transferring energy from said source to said condenserduring the moment of impact of said missile with a target,

a first discharge path for said condenser including a resistance forcausing the voltage on the condenser to decrease at a predetermined rateof time, and a second discharge path for said condenser including anelectroresponsive detonator, a rectifier, atglow tube and a secondcondenser connected in series across the first condenser in the ordernamed, said rectifier having low conductance in the direction of saiddischarge insufiicient to ignite said detonator whereby the energypassed therethrough is stored in the second condenser until said glowtube is extinguished as the difference in the voltages on the condensersbecome equal to or less than the sustaining potential of the glow tube,said rectifier having high conductance in the reverse direction todischarge sufiicient energy therethrough from said second condenser tofire said detonator, said glow tube being rendered conducting todischarge said energy from the second condenser when the difference involtages of the condensers increases to the breakdown potential of thetube upon continued discharge of the first condenser following saidextinguishing of the glow tube.

3. In an electric time fuze of the character disclosed for use in anordnance missile, the combination of a normally charged condenser, anelectroresponsive detonator, impact responsive switch means, a secondcondenser operatively connected to said switch means and to saidnormally charged condenser and adapted to be charged from charge energytherethrough from said third condenser to fire said detonator, said glowtube being rendered conducting to discharge said energy from the thirdcondenser when said diflierence in the voltages -of-the: second andthirdcondensers increases to the breakdown potential of the tube uponcontinued discharge of'the seco'ndcon denser following saidextinguishing of the glow tube.

f 5. An electric timefuze of the character disclosed for; use in anordnance missile comprising, in combination, a

- first normally charged condenser, a second condenser,

the charged condenser as the switch means operates in response to impactof said missile with a target, a resistance connected to said secondcondenser for causing the voltage on the condenser to decrease at apredetermined rate of time, a third condenser operatively connected tosaid first and second condensers and charged thereby,

and a rectifier and a glow tube connected to said second and thirdcondensers for passing energy discharged from said first and secondcondensers to said third condenser through the detonator in an amountinsufiicient to fire the detonator, said rectifier being adapted todischarge the energy from said third condenser through the detonator andrectifier to the second condenser in an amount sufficient to fire thedetonator when the voltage on said third condenser exceeds the potentialof said second condenser by a predetermined amount to render the glowtube conductive. b

4. An electric time fuze of the character disclosed for use in a missilecomprising, in combination, a normally charged condenser, a normallydischarged condenser, 21

normally open discharge path including an impact responsive switch meansdisposed between said condensers for momentarily transferring energyfrom said first condenser to said second condenser as the switch -isactuated from an initial position to a moved position in response to theimpact of the missile with a target, a discharge path for the secondcondenser including a resistance for causing the voltage on the secondcondenser to decrease at a predetermined rate of time, and a seconddischarge means including a normally open charging circuit fortransferring energy from said first condenser to said secondcondenserasthe circuit is closed,impact responsive switch means in said circuitfor closing the circuit momentarily as the switch is actauted from aninitial position to a moved position in response tojimpact of said,missilewit h a target, a first discharge path forsaid, second condensercomprising .a, resistance for causingthe' voltage on thesecond condenserto decreaseata prede-g- I termined rate of time, a,seconddischargepathjfor said If secondcondenser, an electroresponsive detonatorin saidsecond discharge path, a rectifier in said second discharge pathinseries with said 'detonatona glowtube in said second discharge path inseries with said-detonator and" rectifier, a third condenser in saidsecondtdischarge path and connected in series therein with the secondcondenser, detonator, rectifier andglow tube in the order named andcharged therethrough by said first and second condensers as the circuitis closed and by said second condenser when, the circuit thereafter isopened, said rectifier having low conductance in-the direction of saiddischarge therethrough to said thirdcondenser insufiicient' to ignitesaid detonator whereby the energy passed therethrough. is.- stored inthe third condenser. until said iglowtubeisextinguished as thedifference in the voltages on the second and third condensersbecomesequal to or less than the sustaining potentialof the'tube, saidrectifier having high QOfidPctance in the reverse direction sufiicientto'vdis charge energy therethrough from said-third condenser to f firesaidldetonator, said. glow tube being rendered conducting todischargesaid energy from .the third condenser when -said difference in voltagesof the second and-third condensers increases to thebreakdownpotential-of the tube upon continued discharge of the secondcondensers following said extinguishing of the glow tub'ef 6. Anelectricfuze for use 'in an ordnance missile 'comprising a firstcondenser-having a charge thereon received during. impact of the missilewith a target, an electroresponsive detonator, a rectifier having a lowforward resistance and a high reverse resistance, a second condenser, aglow tube, circuit means'for effecting c'harging of said secondcondenser from said first condenser through said detonator, said glowtube and in the reverse directionthroughsaid; rectifier in an amountless than thesustaining potential on the glow"'tube"and insufiicient tofire said, detonator, and a diischargefpath for said first condenser for:reducing'the' voltage thereon in j predetermined time delayed relationto saidimpact, said circuit means forming a discharge pathfor saidsecond condenser for discharging said charge thereon through saiddetonator and in the forward direction through said rectifier in anamount exceeding the sustaining potential of the glow tube: andsutficient to'fire the detonator when the voltage on the secondcondenser exceeds the voltage on the first condenser by a predeterminedamount.

7. An electric time fuze of the character disclosed for use in anordnance missile comprising first, second and third condensers,circuitmeans for charging the first condenser to a predetermined potential asthe missile is launched, impact responsive means for momentarilytransferring energy from said first condenser to said second and thirdcondensers during each of a series of impacts of the missile with aplurality of targets, an electroresponsive detonator, and a rectifierand a glow tube conected in'series in the charging path of the thirdcondenser and connected in series circuit with the third condenseracross the second condenser, and a discharge path for said secondcondenser for reducing the voltage thereon in predetermined time delayedrelation to each of said impacts, said rectifier having a low forwardresistance and a high reverse resistance, said rectifier being connectedin said series circuit with said reverse resistance thereof opposingcharging of the third condenser and limiting the time rate of chargethereof to a value in-- sufiicient to fire said detonator until thevoltage on said condensers are substantially equal and the glow tube isextinguished, said forward resistance of the rectifier beingsufiiciently low to fire the detonator by the discharge of said thirdcondenser therethrough when the voltage on the second condenser hasdropped to a predetermined value below the voltage on the thirdcondenser and said glow tube is rendered conductive following the lastof said impacts.

8. An electric time fuze of the character disclosed for use inafm'issile comprising, in combination, a first normally dischargedcondenser, a source of electrical energy, impact responsive switch meansfor momentarily-transferring energy from said source to said condenserduring the moment of impact of said missile with a target, a firstdischarge path for said condenser including a resistance for causing thevoltage on the condenser to decrease at a predetermined rate of time,asecond discharge path for said condenser, a second condenser in saidsecond discharge path and connected in series therein with said firstcondenser and charged by said voltage as the first condenser isdischarged, an electroresponsive detonator in said second discharge pathincluding a rectifier and glow tube connected-in series therein with thefirst condenser in the order named, a normally closed impact responsiveswitch means in said first discharge path and shunted across a portionof said resistance for momentarily increasing the efiect in resistancein the first discharge path as the normally closed impact switch meansop'ens mo- Inentarily during said impact of the missile, said rectifierhaving low conductance in the direction of said discharge therethroughto the second condenser insufficient to ignite said detonator wherebythe energy passed therethrough is stored in the second condenser untilsaid'glow tube is extinguished as the diiference in the voltages on thecondensers: becomes equal or less than the sustaining voltage of 'theglow tube, said rectifier having high conductance in the reversedirection sufiicient to discharge energy therethrough from said secondcondenser to fire said detonator, said glow tube being renderedconducting to discharge said energy from the second condenser when thedifierence in voltages of the condensers increases to thebreakdownpotential of the tube upon continued discharge of the first condenserfollowing said extinguishing of the glow tube.

9. An electric time fuze of the character disclosed for use in a missilecomprising, in combination, a first norsponsive switch means shuntedacross a portion of said resistance and connected to said source formomentarily transferring energy from said source to said condenser andmomentarily increasing the effective value of said resistance during themovement of impact of said missile with a target, a first discharge pathfor said condenser including the remaining portion of said resistancefor causing the voltage on the condenser to decrease at a predeterminedrate of time when said first resistance portion is shunted followingimpact, a second discharge path for said condenser, a second condenserin said second discharge path and connected in series therein with saidfirst condenser and charged by said voltage as th'efirst condenser isdischarged, an electroresponsive detonator in said second discharge pathincluding a rectifier and glow, tubeconnected in series therein with thesecond con-.

denser in the order named, said rectifier having low conductance in thedirection of said discharge therethrough to the second condenserinsufiicient to ignite said detonator wherebythe energy passedtherethrough is stored the reverse direction sufiicient to dischargeenergy there-.

through from said second condenser to fire said detonator,

said glow tube being rendered conducting to discharge said energy fromthe second condenser when the difference in the voltages of thecondensers increases to the breakdown potential of the tube uponcontinued discharge of the first condenser following saidv extinguishingof the glow tube. V

10. An electric timefuze of the character disclosed for use in anordnance missile comprising first, second and third condensers,circuitmeans for charging the first condenser to a predetermined potential asthe missile is launched, impact responsive circuit means for mome ntarily transferring energy from said first condenser to said second andthird condensers during each of a series of impacts of the missile witha plurality of targets, resistive means in the charging paths of thesecond and third condensers for limiting the time rate of said transferof energy thereto, an electroresponsive detonator, a rectifier and aglow tube connected in series in the charging path of the thirdcondenser and connected in series circuit with the third condenseracross the second condenser, and a discharge path for said secondcondenser or reducing the voltage thereon in predetermined time delayedrelation to each of said impacts, said rectifier having a lowforwardresistance and a high reverse resistance, said rectifier beingconnected in said series circuit with said reverse resistance thereofopposing charging of the third condenser and limiting the time rate ofcharge thereof to a value insufiicient to fire said detonator until thevoltage on said condensers are substantially equal and the glow tube isextinguished, said forward resistance of the rectifier beingsufiiciently low to fire the detonator by the discharge of said thirdcondenser therethrough when the voltage on the second condenser has,

dropped to a predetermined value below the voltage on the thirdcondenser and said glow tube is rendered conductive following the lastof said impacts.

References (Jited in the file of this patent FOREIGN PATENTS 865,507France Feb. 24, 1941

